Most of the manager's chairs are equipped with an adjusting mechanism for adjusting the height of the seat, and some chairs even include an adjusting mechanism for adjusting the backrest to a desired tilt position. Nevertheless, the users are experienced that the arm rests are not adjusted relative to the seat and this cannot provide the users a comfort sitting environment.
As shown in FIG. 7, a conventional adjusting mechanism for adjusting the arm rest for chairs and generally includes an L-shaped frame 1 which includes a plurality of positioning holes 2 defined through the upright portion thereof. A sleeve 3 is movably mounted to the frame 1 and an arm rest 4 is connected to an open top of the sleeve 3. The open top of the sleeve 3 includes two flexible plates 5 connected to a top edge of the wall thereof and an operation member 6 is engaged with the open top of the sleeve 3. The operation member 6 includes a top end engaged with the flexible plates 5 and a hook member 7 extends laterally from a lower end of the operation member 6. The flexible plates 5 provide a biasing force to the operation member 6 to insert the hook member 7 with one of the positioning holes 2 to set the height of the arm rest 4. When adjusting the arm rest 4, the user pushes the operation member 6 to overcome the force of the flexible plates 5 and to remove the hook member 7 from the positioning hole 2, the sleeve 3 is then able to be move relative to the frame 1 till a desired height, the operation member 6 is released and the hook member 7 is engaged to another positioning hole 2.
The operation member 6 is located within the sleeve 3 and is difficult to be assembled. Besides, the whole arm rest unit has to be disassembled if an old part is to be replaced within the sleeve 3. This increases the cost for maintenance.
Because the operation member 6 has to be pushed frequently to adjust the height of the arm rest 4, the conjoint portion between the sleeve 3 and the operation member 6 is easily worn out and the operation member 6 shakes or swings during adjustment, sometimes, the hook member 7 cannot successfully engaged with the positioning hole 2.
Furthermore, when adjusting, the operation member 6 is pushed and the hook member 7 is disengaged from the positioning hole 2, the sleeve 3 can be completely pulled out from the frame 1.